Content-based information retrieval architecture

Abstract

A content-based information retrieval architecture is herein disclosed that can achieve correct and predictable high speed lookups while taking advantage of inexpensive conventional memory components.

Description

[0001] This Utility patent application is a Non-Provisional of and claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 541,983 entitled “INEXPENSIVE AND FAST CONTENT ADDRESSABLE MEMORY” filed on Feb. 5, 2004, the contents of which are incorporated by reference herein.BACKGROUND OF THE INVENTION [0002] The present invention relates to architectures for fast information retrieval. [0003] Content addressable memories (CAMs) are devices that are queried using data in contrast to conventional memories that are queried using addresses. CAMs search through their contents to check if the data exists, and if so, provide information associated with the data. Such memories find applications in Internet routers, processor caches, databases, and other situations where fast lookups are required. Most commercial routers employ CAM devices called Ternary-CAMs (TCAMs) which are specialized memory devices that check if a query matches every entry in parallel. TCAMs are more expensiv...

AI Technical Summary

Benefits of technology

[0011] One advantageous application of the present architecture is in network routers. A network router can be readily constructed using such an architecture to implement a plurality of filters which can perform longest prefix matching on a packet header, where the input value is a prefix of a pre-specified length and the lookup value is the forwarding information. An advantageous design is to utilize a plurality of filters, one for each prefix length operating in parallel. Where several of the filters signal a match, a priority encoder can be used to select the forwarding information from the filter with the longest prefix match. The filters can be implemented in pairs, where an update filter can be updated off-line and swapped for the filter that is performing lookups.

[0012] The content-based information retrieval architecture disclosed herein can be readily implemented in hardware or software or an advantageous combination of both. An implementation advantageously can be embodied in a single chip solution, with embedded memory, or a multi chip solution, with external SRAM / DRAM. The above-described architecture has a number of key advantages over related technologies. As discussed above, the design can use standard inexpensive memory components such as SRAM or DRAM, thereby facilitating ease of manufacture. The design is capable of high speeds, as it uses streaming data with no hardware dependencies and may be deeply pipelined to obtain high throughput. Additionally, the design has the potential to consume significantly less power than equivalent TCAM components. These and other advantages of the invention will be apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings.

Problems solved by technology

For example, where an input value ends up generating a plurality of hashed values that correspond to not one singleton location in the first table of encoded values, this can complicate reconstruction of the table.

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